Stem cells have significant therapeutic potential. In a non-limiting aspect, the present invention is directed to using mesenchymal stem cells to treat eye injuries and diseases. Other non-limiting aspects are directed to the therapeutic use of mesenchymal stem cells for treating diseases which include those of the lung and heart. Another non-limiting aspect of the present invention is directed to the use of anti-apoptotic and anti-inflammatory proteins such as STC-1 and TSG-6, which are expressed by mesenchymal stem cells, for treating the above-mentioned diseases and disorders.
The cornea, apart from being an important component of the refractive system of the eye, serves as a biologic and physical barrier by protecting the interior structures of the eye from environmental insults. The transparency of the cornea and, consequently, visual acuity are both dependent upon the integrity and functionality of the outermost layer, the epithelium. Most of the diseases occurring in corneal epithelium (i.e., corneal surface diseases) are accompanied by sterile inflammation and defects in wound healing. Therapies for these diseases remain problematic.
The most severe form of corneal surface diseases is limbal epithelial stem cell deficiency (LSCD). It can be primary as a result of inherited eye disease, but more commonly it is the result of acquired conditions such as chemical or thermal burn injuries, systemic autoimmune disease, contact lens keratopathy, recurrent ocular surgeries, or Stevens-Johnson Syndrome (SJS). The incidence of chemical burns is 500,000 cases per year and accounts for 7 to 18% of the 2.5 million cases of ocular trauma seen in emergency departments each year in the U.S. (Melsaether et al., 2009). The annual incidence of SJS that causes severe LSCD is 2.6 to 7.1 cases per 1 million people or about 200,000 people in the U.S. population (Foster et al., 2008). LSCD not only inflicts enormous psychological stress on patients, but it also carries an economic burden in terms of loss of productivity and prohibitive health care costs over the lifetime of the patients.
The current treatments of LSCD include anti-inflammatory drug therapy (e.g. steroids) in the early phase and transplantation of limbal epithelial stem cells (LESCs) in the late stage (Limb and Daniels, 2008). However, the anti-inflammatory drugs currently available are disappointing and are unable to prevent subsequent loss of LESCS. The current strategies for correcting LSCI by transplanting LESCs from a patient's healthy eye (limbal autograft), a living-relative, or cadaveric donors (limbal allograft) have many drawbacks (Ilari et al. 2002; Solomon et al, 2002; Cauchi et al. 2008). The limbal autograft carries the risk of creating LSCD in the donor eye (Jenkins et al., 1993) and cannot be used in patients with bilateral LSCD. Limbal allografts require long-term systemic immunosuppression because of the presence of HLA-DR antigens and Langerhans cells in the graft. Even with immunosuppression, immunological rejection occurs in 42.9% to 64.0% patients after limbal allografts (Rao et al., 1999; Tseng et al., 1998; Shi et al., 2008; Reinhard et al., 2004; Tsubota et al., 1999). Currently, ex vivo cultivation and transplantation of LESCs are being used for LSCD in some centers (summarized in Shortt et al., 2007). However, the putative stem cells observed in the limbus have not yet been reproducibly isolated or fully characterized. Moreover, the main clinical limitation for using cultured LESCs therapeutically is the availability of an autologous donor tissue. Although cultured allogeneic cells may be used in combination with systemic immunosuppression, donor allogeneic LESCs do not survive beyond a period of 9 months (Daya et al., 2005; Sharpe et al., 2007). Effective suppression of inflammation at the ocular surfaces is critical for success. Therefore, the therapies that are the goal of the present application can provide an important advance to the current therapy.
In addition to vision-threatening LSCD, there are a number of ocular surface diseases accompanied by corneal inflammation and defects in wound healing, such as keratoconjunctivitis sicca, recurrent corneal erosion, or post-refractive surgery keratitis. The most common is dry eye syndrome that affects nearly 10% of the U.S. population (Moss et al., 2000; Sehaumberg et al., 2003; Moss et al., 2008). As many as 20 to 30 million people in the United States have exhibited early signs or symptoms of dry eye, and an estimated 6 million women and 3 million men suffer from advanced effects of dry eye that alter the quality of life (Mertzanis et al. 2005; Miljanovic et al., 2007). Unfortunately, most of the currently-available therapeutic agents are only palliative and none of them abolish signs and symptoms of dry eye completely (Pflugfelder, 2007). Several studies (Clegg et al., 2006; Reddy et al., 2004; Callaghan et al., 2007) have established that the economic impact of dry eye syndrome is also substantial, in terms of both direct medical costs (e.g. for medications and physician visits) and indirect costs (e.g. lost work time and impaired productivity). In effect, there are no efficient and safe therapeutic strategies for diseases of the corneal surface.
Retinal degenerations, including age-related macular degeneration (AMD) and retinitis pigmentosa (RP), are the leading causes of legal blindness in the United States. AMD and RP share clinical and pathologic features including end-stage blindness due to photoreceptor and/or retinal pigment epithelium (RPE) cell death. Of special importance is that apoptosis of photoreceptors has been shown to be a prominent feature of human AMD (Dunaief, et al., Arch. Ophthalmol., Vol. 120, No. 11, pgs. 1435-1442 (2002); Xu, et al., Trans. Am. Ophthalmol. Soc., Vol. 94, pgs. 411-430 (1996)). and RP (Cottet, et al., Curr. Mol. Med., Vol. 9, No. 3, pgs. 375-383 (2009); Doonan, et al., Curr. Neurosci. Res., Vol 1, No. 1, pgs. 47-53 (2004)) and is the underlying feature in many of the animal models of retinal degeneration (Doonan, 2004; Yu, Invest. Ophthalmol. Vis. Sci., Vol. 45, No. 6, pgs. 2013-2019 (2004); Katai, et al., Invest. Ophthalmol. Vis. Sci., Vol. 40, No. 8, pgs. 1802-1807 (1999); Katai, et al., Jpn. J. Ophthalmol., Vol 50, No. 2, pgs. 121-127 (2006)). Reactive oxygen species (ROS) have been implicated in the initiation and/or exacerbation of cell death in AMD (Fletcher, et al., Ophthalmic Res., Vol. 44, No. 3, pgs. 191-198 (2010); Beatty, et al., Surv. Ophthalmol., Vol. 45, No. 2, pgs. 115-134 (2000); Winkler, Mol. Vis., Vol. 5, pg. 32 (1999); Johnson, Curr. Opin. Cln. Nutr. Metab. Care, Vol. 13, pgs. 28-33 (2010); Totan, et al., Curr. Eye Res., Vol. 34, No. 12, pgs. 1089-1093 (2009)) and antioxidant vitamin therapy is currently one of the mainstays of treatment in non-exudative AMD and RP (Johnson, 2010; Hartong, et al., Lancet, Vol. 368, pgs. 1795-1809 (2006)). Although not curative, reduction of risk of disease and stabilization of vision have been observed following antioxidant vitamin therapy (Flectcher, 2010; Beatty, 2000; Johnson, 2010; Hartong, 2006). Moreover, two of the top modifiable risk factors in AMD-smoking and light exposure—are thought to injure photoreceptors or RPE through ROS-mediated damage (Flectcher, 2010; Johnson, 2010). In addition, oxidative damage studies in animal models of RP have implicated ROS as partially responsible for the apoptotic loss of photoreceptors (Komeima, et al., Proc. Nat. Acad. Sci., Vol. 103, No. 30, pgs. 11300-11305 (2006); Shen, et al., J. Cell. Physiol., Vol. 203, No. 3, pgs. 457-464 (2005)). Further evidence includes studies demonstrating that antioxidant based therapies slow photoreceptor death in animal models of RP (Komeima, et al; J. Cell. Physiol., Vol. 213, No. 3, pgs. 809-815 (2007); Galbinar, et al., J. Ocul. Pharmacol. Ther., Vol 25, No. 6, pgs. 475-482 (2009); Chen, et al., Nat. Nanotechnol., Vol. 1, No. 2, pgs. 142-150 (2006)) and decrease primary retinal cell (Chen, 2006; Chucair, et al., Invest. Ophthalmol. Vis. Sci., Vol. 48, No. 11, pgs. 5168-5177 (2007)) or RPE cell death in vitro (Cao, et al., Exp. Eye Res., Vol. 91, No. 1, pgs. 15-25 (2010); Kim, et al., Invest. Ophthalmol. Vis. Sci., Vol. 51, No. 1, pgs. 561-566 (2010)). Photoreceptors are sensitive particularly to oxidative stress for several reasons: (a) oxygen consumption by the retina is greater than any other tissue (Beatty, 2000); (b) photoreceptor outer segments reside near a rich vascular supply and contain high concentrations of polyunsaturated fatty acids (PUFAs) that undergo oxidation when oxygen is present (Winkler, 1999); (c) lipofuscin accumulates in the RPE during aging and is thought to be a source of ROS that is toxic to the RPE (Beatty, 2000); and (d) photoreceptors are subject to repeated photochemical injury, a process known to produce ROS (Beatty, 2000). These findings in conjunction with our preliminary data provide a strong rationale to test new stem cell based therapies known to reduce ROS-mediated apoptosis in currently incurable degenerative diseases of the retina.
Inflammation is being shown increasingly to play a role in a number of diseases, such as in myocardial infarction, stroke, Alzheimer's disease and atherosclerosis, for example. Thus, the present invention in a non-limiting aspect, is directed to the use of mesenchymal stem cells and the role of certain proteins, such as TSG-6, in treating myocardial infarction and lung diseases.
In summary, there are no effective drugs to treat corneal inflammation and ulceration caused by chemical injury to the cornea. In addition, there is a need for additional therapies for macular degeneration. There also are needs for additional therapies for diseases of the lung and heart. Thus, the present invention is directed to the use of mesenchymal stem cells and stem cell proteins as therapeutic agents.